ANSWER is Propane and butane.The petroleum gas liquefied under pressure is called liquefied petroleum gas(LPG). Liquefied petroleum gas consists of propane and butane.Liquefied petroleum gas is used as fuel for home and industry.The CHEMICAL which is added to liquefied petroleum gas(LPG) to detect leakage is ETHYL mercaptan.Liquefied petroleum gas used for domestic applications in cylinders under relatively low pressures.Liquefied petroleum gas can be STORED nearly indefinitely without degradation. The molecular formula of butane is C4H10.The molecular formula of propane is C3H8.